Another Turboprop Stalls on Short Final

Kenn Borek Air Flight KBA 103 — a Beechcraft King Air 100 with 10 souls on board — crashed on Oct. 25, 2010, during an RNAV (GNSS) approach to Runway 08 at Kirby Lake Airport (CRL4), Alberta, Canada. The airplane struck the ground some 174 ft. short of the threshold, then bounced and came to rest off the edge of the runway. The captain was fatally injured. The first officer and three passengers suffered serious injures, and the five additional passengers suffered minor injuries.

Canada's Transportation Safety Board (TSB) investigated this accident. While the TBS does not issue a “probable cause,” it does issue “findings” as to causes and risks and it reports on safety actions taken. In this incident, the TSB concluded that the crew stalled the airplane after descending below MDA and that the pilots' “conduct . . . during the instrument approach prevented them from effectively monitoring the performance of the aircraft.” The investigators also determined that the stall warning horn did not activate, thus depriving the crew of at least one opportunity to avoid the stall.

The TSB's “findings of risk” — actions that were seen in the review of this flight that could set the stage for an accident sequence — included:

The use of company standard weights and a non-current aircraft weight and balance report that resulted in the flight departing at an inaccurate weight. This could result in a performance regime that may not be anticipated by the pilot.

Flying an instrument approach using a navigational display that is outside the normal scan of the pilot increases the workload during a critical phase of flight.

Flying an abbreviated approach profile without applying the proper transition altitudes increases the risk of controlled flight into obstacles or terrain.

Not applying cold temperature correction values to the approach altitudes decreases the built-in obstacle clearance para–meters of an instrument approach.

The Accident

The day began for the crew when they arrived at KBA's Calgary International Airport (YYC) hangar at 0630 to prepare the King Air for the first leg to Edmonton City Centre Airport (YXD). They departed at 0845 with two passengers and arrived at YXD at 0936.

Eight passengers were boarded at Edmonton for the Kirby Lake leg. Prior to departure, the flight crew checked the weather conditions at Kirby Lake via an online service. They determined that conditions at Kirby Lake were not within the applicable limits to attempt the flight. The flight was delayed until 1016 when ceiling and visibility had improved. The King Air departed Edmonton at 1020.

Approximately 35 nm from Kirby Lake, the crew began to prepare for the RNAV instrument approach to Runway 08. Investigators said the crew engaged in a nonessential conversation — discussions not related to the operation of the aircraft — during the descent and approach to Kirby Lake. KBA 103 was cleared out of controlled airspace to conduct an instrument approach. Weather conditions near the time of the occurrence (1110) were: wind, 170 deg. T at 8 kt. gusting to 16 kt.; visibility, 4 sm in light snow, overcast ceiling at 600 ft. AGL; temperature, 3C, dew point, -4C.

The first officer was the pilot flying (PF) and flew an autopilot-coupled approach from the right seat. The GPS track information was only fed into the left-side HSI. So the first officer obtained lateral track information from the panel-mounted GPS unit in the center of the instrument panel.

This cross-panel view increased the instrument scan workload for the PF, said investigators. The flight proceeded toward the ROPRO waypoint (see accompanying approach plate) from the south with the intent of continuing to the DEDEK waypoint. During the descent, the crew began to encounter light to moderate icing conditions and elected to fly directly to the XIKIB waypoint on a track of 078 deg. M, bypassing the DEDEK waypoint and continuing the descent to 3,500 ft. ASL. Having deviated from the approach profile, the minimum sector altitude of 3,800 ft. ASL would have been applicable.

The approach profile was flown at 140 KIAS due to icing conditions. Anti-icing equipment was active and the deicing boots were activated six times during the approach. The flaps were set at the approach detent (12.9 deg.) and the crew confirmed that the RNAV 08 approach was loaded into the GPS unit and performed a RAIM check. They extended the landing gear and moved the propellers to fine pitch.

As KBA 103 approached the AXAXA final approach waypoint (4.9 nm from the threshold of Runway 08) the captain said he would be looking outside in order to locate the airport.

The approach procedure allows a descent to 2,760 ft. to the MDA after crossing AXAXA. The crew had agreed to round off the MDA to 2,700 ft. ASL. Neither crewmember made the required calls of 100 ft. prior to 2,700 ft. ASL or passing through and descending below 2,700 ft. ASL. (The outside surface temperature was -3C. A cold temperature correction was not applied to the altitudes on this approach; if it had been, the MDA would have been corrected to 2,796 ft. ASL — 536 ft. AGL.)

At approximately 4 nm from the threshold of Runway 08, the captain called the runway in sight; however, the first officer (PF) was not able to identify the runway. Throughout the remainder of the approach, both pilots were predominantly looking outside of the aircraft. The GPS course deviation indicator indicated that KBA 103 was slightly right of track. The PF disconnected the autopilot and proceeded to re-intercept the inbound track, flying the aircraft by hand.

Approximately 3 nm from the runway, the captain identified the road that led to the airport, indicating that the runway was to the left of the road. At about 1 mi. final, the captain pointed out the radio tower to the right of the runway (located midfield); however, the PF still did not have the runway in sight. Shortly thereafter, the PF identified the runway. Approximately 14 sec. later, the airplane's left wing dropped and the crew lost control of the aircraft. There was no audible warning to the approach of a stall. Maximum power was applied, but recovery was not achieved prior to the aircraft hitting the ground.

The left wing made initial contact and the fuselage impacted the ground in a tail-low attitude on a level, grass- and scrub-covered field that ended with a 17-ft. uphill slope to the runway threshold. The King Air bounced and ultimately came to rest on the left edge of the runway, facing the opposite direction. The total length of the wreckage trail was 439 ft.

The left wing and cockpit were substantially damaged. The cabin remained intact, although three seats broke free. Two passengers were able to evacuate via the emergency exit on the right-hand side. The remaining passengers evacuated through the main cabin door on the left side. The first officer was able to extract himself from his seat and was assisted from the aircraft by the passengers. The captain remained in the left seat until emergency medical services personnel were able to extricate him from the aircraft. Local personnel on the airport apron initiated an emergency response; emergency medical services personnel treated the injured occupants until they were transported to medical facilities. A small, post-impact, electrical fire ignited in the front, left-hand side of the cockpit area. Passengers and first responders used handheld fire extinguishers to put it out.

The investigation determined that the engines were producing high power at impact. Propeller blade marks on the ground indicated that the aircraft impacted the terrain at an approximate ground speed of 108 kt. Damage to the aircraft suggests that it experienced a low-energy impact.

The TSB’s Analysis

The TSB focused its analysis on crew performance during the periods when the pilots engaged in non-operational conversation and when both pilots directed their attention outside the cockpit in attempts to obtain visual reference to the runway “at the expense of monitoring the aircraft.” Here's what the TSB had to say:

During the initial stages of the approach to Kirby Lake, the crew was engaged in a conversation that did not directly pertain to the operation of the flight. The casual nature of the conversation between the PF and PNF suggests that they were not overly concerned with the approach and may not have been at a heightened level of attention.

While a majority of the SOP and checklist items were completed during the approach, a number of critical items, such as descending below the minimum sector altitude while diverting to the XIKIB waypoint and failing to announce/confirm the arrival at the MDA, were indicative of lapses in cockpit discipline. The Kenn Borek SOP states that there should be no conversation other than that required for assigned work or for the operation of the aircraft during the descent from 3,000 ft. AGL or top-of-descent, which ever occurs last.

Beyond the distraction within the cockpit, the crew was faced with the additional task of identifying the runway. Although the company SOP did not specify when the PNF should look outside, the automated weather observation system at Kirby Lake indicated that the visibility was 4 sm in light snow. This likely prompted the PNF to look outside of the cockpit at a GPS distance of 4 nm and to identify the runway.

This declaration prompted the PF to look up from monitoring the flight instruments in an attempt to identify the runway. For the remainder of the flight, both crewmembers were focused outside the cockpit. With neither pilot monitoring the airspeed and altitude, the aircraft continued to descend. From the initial identification of the runway, the airspeed decreased to a point that it entered an aerodynamic stall. The aircraft was, however, too low to effect a recovery, despite attempts by the crew to do so.

The loss of control of the aircraft was likely the result of a stall or near stall condition. The ground speed determined by the propeller marks and the high engine power setting during the attempted recovery indicate that the aircraft was in a low energy state. The aircraft's close proximity to the ground prevented a full recovery from the loss of control.

Pilots are often expected to perform a number of concurrent activities. In this case, this involved flying and monitoring the aircraft as well as visually acquiring the runway. During these multitasking situations, the crew may prioritize activities based on their perceived level of importance. In this case, the act of visually finding the runway was categorized as being of primary importance. As such, the crew's cognitive efforts were directed to this activity at the expense of monitoring the flight profile.

The aircraft was equipped with a stall warning system, which did not activate prior to the aircraft entering a low energy state. The aircraft's wing deicing system appeared to be functional throughout the approach and the post-impact inspection of the aircraft did not indicate an accumulation of ice on the critical flight surfaces. The investigation was unable to determine why the stall warning system did not activate.

Final Thoughts

Kenn Borek Air Ltd. has taken the following safety actions:

Amended the weight and balance calculation procedure to require flight crews to confirm the correct aircraft configuration and passenger weights.

Implemented a company line check program to ensure adherence to SOPs including sterile cockpit procedures.

Developed and implemented a procedures review exam for flight crew, emphasizing SOP and company procedures for stabilized approaches, sterile cockpit, and crew roles and duties during non-precision approaches at remote airports with limited services.

Amended company SOP and placarded aircraft equipped with a Garmin 155XL regarding conducting GPS approaches. These approaches will be flown from the left seat only.

When all is said and done, this accident reflects the old maxim that a pilot's responsibilities are to aviate, navigate and communicate — in that order. Somebody has to be flying the airplane at all times and that includes monitoring airspeed, altitude, configuration and performance. It doesn't matter where the runway is if you don't have enough airspeed to remain aloft until you reach it.